fn main() {
    println!("Hello, world!");

    another_function();
    function_with_parameter(100, true);

    let ret = function_with_return(200);
    println!("ret: {ret}");

    let ret = function_with_return2(300);
    println!("ret: {ret}");
}

fn another_function() {
    println!("another_function");
}

fn function_with_parameter(x: i32, y:bool) {
    println!("function_with_parameter: {x}, {y}");
}

fn function_with_return(x:u32) -> u32 {
    println!("function_with_return");
    x
}

fn function_with_return2(x:u32) -> u32 {
    println!("function_with_return2");
    return x;
}

fn function_with_return3(x:u32) -> u32 {
    println!("function_with_return2");
    x; // 语句
}